Collaborative Research: Optical Transitions in Metallic Nanoclusters at High Pressure

非技术总结这项研究计划有助于纳米材料的创新，这些创新在生物医学治疗、传感和催化中很有用。由少于200个金属原子组成的纳米团簇因其近红外光发光、生物相容性和超小尺寸而受到人们的关注。这些纳米团簇的结构和光学性质之间的关系尚不清楚，这阻碍了具有优化性能的纳米团簇的设计。该计划利用压力来改变纳米团簇的结构，以了解负责光吸收和发光的电子跃迁，以及纳米团簇在外部刺激下的稳定性。这项研究与我们的教育计划紧密相连，通过培训博士后和研究生，通过支持K-12和大学一级的科学和技术水平的代表不足的群体，以及通过支持社区的科学教师。此外，在本课程中，解释力学对光学行为的影响的模块将被纳入本科生课程。技术总结拟议的研究涉及使用钻石顶压腔技术来表征由金或银加上配体组成的原子精确团簇的性质，并通过光学测量(吸收和发射)来研究激发态。这些实验将使用电子结构理论进行建模，包括确定结构的基态计算和确定光学性质的激发态研究，并包括基于二次线性响应理论和区域分离密度泛函理论的方法开发。这项研究的目的是识别光学性质，如等离子体激子到激子的跃迁，以及发光效率随着压力的增加而增加；这两种性质对于在实际应用中使用团簇都是有意义的。这项研究包括三个研究目标：(1)研究压力下团簇材料的广泛吸收和近红外发光的能量传递；(2)确定纳米团簇异常多次发射的来源；(3)研究2-3 nm纳米团簇，以表征从等离子体到激子状态的转变。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis research program contributes to innovations in nanomaterials that are useful in biomedical therapies, sensing, and catalysis. Nanoclusters that consist of fewer than ~200 metallic atoms are of interest due to their luminescence in near-infrared light, bio-compatibility and ultra-small size. The relationship between the structure and optical properties of these nanoclusters remains unclear, which prevents the design of nanoclusters with optimized performance. This program uses pressure to modify the structure of nanoclusters, in order to learn about the electronic transitions that are responsible for light absorption and luminescence, as well as the stability of nanoclusters under external stimulus. This research is closely tied to our educational plans through the training of postdocs and graduate students, by supporting underrepresented groups at the K-12 and college level in science and technology, and by supporting science teachers in the community. In addition, modules that explain the influence of mechanics on optical behavior will be incorporated into undergraduate courses during this program.TECHNICAL SUMMARYThe proposed research is concerned with characterizing the properties of atomically precise clusters composed of gold or silver plus ligands using diamond anvil cell techniques to apply high pressure, and with optical measurements (both absorption and emission) to study excited states. The experiments will be modeled using electronic structure theory, including ground state calculations to determine structures, and excited state studies to determine optical properties, and including methods development based on second linear response theory and domain-separated density functional theory. The research is aimed at identifying optical properties such as plasmon to exciton transitions, and an increase in luminescence efficiency with increasing pressure; both properties are of interest to using the clusters in practical applications. The research includes three research objectives: (1) study of energy transfer responsible for broad absorption & near-infrared luminescence of the cluster material under pressure, (2) determine the source of anomalous multiple emissions of the nanoclusters, and (3) studies of 2-3 nm nanoclusters to characterize the transition from plasmonic to excitonic states.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.